AN 8.63 4sp, 4bv, 4j all are part of "3 ways of samadhi" (samādhi in 3 ways), and you can do any combination of those in all four postures. Also see AN 3.63 for explicit tie between 4j and walking. AN 8.63 is like an expanded version of SN 47.3 + SN 47.4.